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High Energy Physics - Phenomenology

Title:
Dimension-six electroweak top-loop effects in Higgs production and decay

Abstract: We study the next-to-leading order electroweak corrections to Higgs processes
from dimension-six top-quark operators in the Standard Model Effective Field
Theory approach. We consider the major production channels, including $WH$,
$ZH$, and VBF production at the LHC, and $ZH$, VBF production at future lepton
colliders, as well as the major decay channels including $H\to \gamma\gamma,
\gamma Z, Wl\nu,Zll,b\bar b,\mu\mu,\tau\tau$. The results show that within the
current constraints, top-quark operators can shift the signal strength of the
loop-induced processes, i.e. $H\to \gamma\gamma,\gamma Z$, by factors of
$\sim\mathcal{O}(1)-\mathcal{O}(10)$, and that of the tree-level processes,
i.e. all remaining production and decay channels, by $\sim5-10\%$ at the LHC,
and up to $\sim15\%$ at future lepton colliders. This implies that essentially
all Higgs channels have started to become sensitive to top-quark couplings, and
in particular, Higgs observables at high luminosity LHC as well as future
lepton colliders, even below the $t\bar t$ threshold, will improve our
knowledge of top-quark couplings. We derive the sensitivities of Higgs
measurements to top-quark operators at the high luminosity LHC, using
projections for both inclusive and differential measurements. We conclude that
treating the dimension-six top-quark sector and the Higgs/electroweak sector
separately may not continue to be a good strategy. A global analysis combining
Higgs and top-quark measurements is desirable, and our calculation and
implementation provide an automatic and realistic simulation tool for this
purpose.